[GamePlay] Ascension and Karthus' passive

I recently played a game in Ascension where the enemy had a karthus. During the game I was playing shaco and he was attacking the ascendant in the middle. I assassinated him just as the ascendant died and karthus' passive activated meaning Karthus had died. The powerup dropped and because nobody picked it up and Karthus was in the middle, albeit dead, he got it and grew to full HP. I don't believe this is a proper gameplay function.